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Topic: Y'all are really good at spotting front or back focus in photos... (Read 5617 times)

And today was the first real opportunity I had to go and play with my new 70-200mm f2.8L is mkii. so if y'all don't mind looking at some zoo photos. this was just a test. I had it on aperture priority all day and I should have kicked up the iso to 1200+ when I was indoors, but I wass lazy and didn't bother. so they aren't perfect, and I'm really impressed with the lens.

at the moment I have a 60d, so no afma, but I will be upgrading to a 5d mkiii soon. so if it is a bit front focused, I will eventually be able to correct that without issue.

Were you focusing on the eye? If so, its front focused. This might also be caused by focus being messed up by the glass.

If you change cameras, focus will not be the same, it might back focus, or be perfect.

Test the lens on a subject that allows complete control of the area in focus, like a brick wall at 90 degrees. You must know exactly where the camera tried to focus, and the little red square does not guarantee it.

If its off noticeably, ask Canon to calibrate the lens on their reference 60D.

Were you focusing on the eye? If so, its front focused. This might also be caused by focus being messed up by the glass.

If you change cameras, focus will not be the same, it might back focus, or be perfect.

Test the lens on a subject that allows complete control of the area in focus, like a brick wall at 90 degrees. You must know exactly where the camera tried to focus, and the little red square does not guarantee it.

If its off noticeably, ask Canon to calibrate the lens on their reference 60D.

I always focus the AF point on the eye. I think I was using one of the peripheral AF points. I was using AI Servo... and there wasn't any motion...

The lion shot nobody could have gotten in Servo mode. No matter if you have the AF point exactly on the eye, the sensor is too big and it will almost always pick to focus down the nose, which is closer, and the nose going away from the face creates more contrast. In that shot try One Shot mode, with small AF point activated, which even still might be too large.

The lion shot nobody could have gotten in Servo mode. No matter if you have the AF point exactly on the eye, the sensor is too big and it will almost always pick to focus down the nose, which is closer, and the nose going away from the face creates more contrast. In that shot try One Shot mode, with small AF point activated, which even still might be too large.

If its off noticeably, ask Canon to calibrate the lens on their reference 60D.

The af on the 60d isn't very precise, I am very often shooting animals and af'ing the eyes with thin depth of field (so servo af is of no use) but I have to take 2-3 shots to get it right, it's often just a little behind or in front. You get best results on 60d if af'ing from a way out of focus position and not near the intended focus, btw.

For determining real persistent front/backfocus you have to take the pain to take some shots of a tilted scale, focus with lv contrast & then with phase af and look for any difference in a particular direction.

It's best not to worry about it much on the 60D unless you plan to send it in. The center AF point is too large to pick up the eye as some have suggested unless you have a full frame head shot. Also in evaluating AF adjustments, never use AI Servo. always one shot. The nature of AI servo (and particularly with the 60D) is that the AF will do a lot of hunting even when the subject is still. With the 5D3 that is improved with the 70-200 2.8L IS II due to the closed loop AF feedback you will get with the combo. the lens will report back it's position to the camera as confirmation that it's there. WIthout the feedback the camera needs to shift the focus back and forth around the focus point to tell where the lens actually is. It's very fast but often leaves you with less keepers..which is why in AI Servo you should use Drive mode and let 4 or 5 shots or more rip...you can sort out the sharp ones later.

The nature of AI servo (and particularly with the 60D) is that the AF will do a lot of hunting even when the subject is still. With the 5D3 that is improved with the 70-200 2.8L IS II due to the closed loop AF feedback you will get with the combo. the lens will report back it's position to the camera as confirmation that it's there. WIthout the feedback the camera needs to shift the focus back and forth around the focus point to tell where the lens actually is. It's very fast but often leaves you with less keepers..

Off topic, but out of interested: Does anyone know if the 6d has these closed loop improvements like the 1dx/5d3? I know the 6d cannot use the improved precision of the latest lenses, but its precision has gone up some from the 5d3 and I could not find anything about it being closed loop or not.

I always focus the AF point on the eye. I think I was using one of the peripheral AF points. I was using AI Servo... and there wasn't any motion...

I also have to ask... Why were you using Servo? Servo is meant for subjects in motion. In the case of the lion, it's pretty clear she's not going anywhere. Personally, I only use Servo when shooting a moving subject where I want to rattle off several photos in the hope that at least one of them will turn out. Servo can be very jumpy, even on a stationary subject. So it's going to be almost impossible to determine AF front/back focusing when the photos you're analyzing were shot it anything other than single shot AF using only your center AF point.

If you're primarily using Servo and are getting AF inconsistency, switching to single shot AF will solve most of your problems.

I always focus the AF point on the eye. I think I was using one of the peripheral AF points. I was using AI Servo... and there wasn't any motion...

I also have to ask... Why were you using Servo? Servo is meant for subjects in motion. In the case of the lion, it's pretty clear she's not going anywhere. Personally, I only use Servo when shooting a moving subject where I want to rattle off several photos in the hope that at least one of them will turn out. Servo can be very jumpy, even on a stationary subject. So it's going to be almost impossible to determine AF front/back focusing when the photos you're analyzing were shot it anything other than single shot AF using only your center AF point.

If you're primarily using Servo and are getting AF inconsistency, switching to single shot AF will solve most of your problems.

Because I was being lazy. I think we were at the monkees prior and they were moving... so user error due to laziness.